What's new in JACK2 - Linux Audio...

What’s new in JACK2

Stephane Letz, Nedko Arnaudov, Romain Moret

Linux Audio Conference : april 16, 2009

Post LAC 2008 state

Desirable goals from LAC 2008 ”The Future of JACK meeting”

Startup & configuration : a bit of workNetJack : yes in progressDesktop integration : yes in progressInternal design : yes in progressClient programming and API : yes in progress

Not anticipedExternal contacts and developmentsSolaris version with new ”profiling” tools

What has been done?

2008 DevelopmentsInternal design : code restructuration (Grame)Server control API : (Nedko Arnaudov, Grame)D-Bus based server control (Nedko Arnaudov, JuusoAlasuutari, Grame)NetJack2 (Romain Moret, Grame)”Profiling” tools (Grame)Solaris version (Grame)

OtherExternal contacts : RTL, CopperLan, Native InstrumentsOSX and Windows specific toolsFuture developments (MIDI, ”pipelining”, control...)?

Internal design

GoalsCleanly separate server and client side servicesDefine a server control APIImprove server internal clients (example of use inNetJack2)

Server and client side libraries

Server sidelibjackserver : JACK API (opens client as ”internal” in theserver...) + control APIused by backends and internal clientsused by ”jackd” and new ”jackdbus” control applicationsallows an application to embed the server in it’s process

Client sidelibjack : JACK API (opens client in separated processesusing IPC...)used by client applications

Control API

Objectivesdynamically retrieve server control parameters, backendand internal clients parameters, get/set their valuescreate/destroy the serverstart/stop the server with a given backendload/unload internal clientsnow used by ”jackd”

Internal clients

How are they controled and loaded?

using the ”old” way (with jack load -i ”parameters” andjack unload)

using the new control API way : jackctl server load internaland jackctl server unload internal

D-Bus description

What is D-Bus?a simple inter-process communication (IPC) systemprograms register for offering services to othersclients look up which services are available

D-Bus server control access

D-Bus server control accessjackdbus executable to start D-Bus servicebehaves as an interface between D-Bus system and theJACK server, to use JACK control API with D-Busserver autostart done by libjack using control D-Businterface

D-Bus server control access

Exported interfacesjackdbus controller object export several interfacesconfigure the server (parameters access)control the server (start/stop)”patchbay” : improved graph state access (connections,notification of changes...)jack control python control toolbetter presented in Juuso presentation on LASH

NetJack2

Designsimplify the usability modelredesign for easier multi-platform supportcurrently developed for LAN only

Componentskeep the master/slaves modelnetmanager (master) and jack net bakend (slave)”adapters” : audioadapter and netadapter

Netmanager

Life cycleloaded as an internal clientwaiting for slaves on a multi-cast addresscreate ”proxy” internal clients for each slave, withrequested number of in/out audio and MIDI ports”proxy” ”automatically” appear and disappear when slavescome and go

Net backend

Life cycleappears as ”available”, server is running in ”dummy” mode(clients can connect...)connecting to master, describes it’s parameters : in/outports...retrieve sample rate and buffer size from the masterstarts processingif master disappear, go back in ”dummy” mode

Example of setup

Data streams

Data streamaudio and MIDIlatency control (using ”fast”, ”normal”, ”slow” transmissionmodes...)number of in/out audio/MIDI ports, address, UDP port,MTU parameters

Adapters

Adapting network to audio interfaceaims at ”adapting” (sample rate, buffer size, clock drift...) anetwork stream on an audio interfaceaudioadapter : adapts a slave synched on Net backend onit’s audio card (generalisation of alsa in/out)a version on each plafform (Linux/ALSA, OSX/CoreAudio,Windows/PortAudio, Solaris/OSS)netadapter : adapts the network stream on a slave runningan audio backend

Adapters

Net backend

Master net « proxy »

Audio adapter Audio card

SLAVE

MASTER

Netadapter

Master net « proxy »

Audio backend Audio card

SLAVE

MASTER

Audioadapter Netadapter

Adapters

How does they work?”produces/consumer” model using an intermediate ringbufferresampling if needed (using libsamplerate)resampling ratio dynamically adjusted using Torben HohnPI controler (JACK1)

”Profiling” tools

Objectivesrecord timing informations when graph is runningtiming of backend, signal, wake-up, end date of each clientcompute scheduling latency and client durationgenerate log files and visualization scripts for GnuPlot

Audio driver interrupt

Duration between successives audio interrupts64 frames, 48 kHz, regular interrupt

1290

1300

1310

1320

1330

1340

1350

1360

1370

0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000

usec

audio cycles

Audio driver timing

Audio period

Audio driver interrupt

Duration between successives audio interrupts64 frames, 44.1 kHz, non regular interrupt

1200

1400

1600

1800

2000

2200

2400

2600

2800

0 200 400 600 800 1000 1200 1400 1600

usec

audio cycles

Audio driver timing

Audio period

Driver end date

Duration between start and end of cycle at driver level64 frames, 48 kHz, asynchronous mode

0

20

40

60

80

100

120

140

160

180

0 10000 20000 30000 40000 50000 60000 70000

usec

audio cycles

Driver end date

Driver end date

Driver end date

Duration between start and end of cycle at driver level64 frames, 48 kHz, synchronous mode

0

200

400

600

800

1000

1200

1400

0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000

usec

audio cycles

Driver end date

Driver end date

Clients end date

End date of all clientshere at 64 frames, 48 kHz

0

200

400

600

800

1000

1200

1400

0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000

usec

audio cycles

Clients end date

Audio periodjack_simple_client

ethersonikethersonik-01ethersonik-02ethersonik-03ethersonik-04ethersonik-05ethersonik-06ethersonik-07ethersonik-08ethersonik-09

Clients scheduling latency

Duration between signal date and actual wake-up datehere at 64 frames, 48 kHz

0

50

100

150

200

250

300

350

400

450

500

0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000

usec

audio cycles

Clients scheduling

jack_simple_clientethersonik

ethersonik-01ethersonik-02ethersonik-03ethersonik-04ethersonik-05ethersonik-06ethersonik-07ethersonik-08ethersonik-09

Clients duration

Duration between wake-up date and end datehere at 64 frames, 48 kHz

0

50

100

150

200

250

300

350

0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000

usec

audio cycles

Clients duration

jack_simple_clientethersonik

ethersonik-01ethersonik-02ethersonik-03ethersonik-04ethersonik-05ethersonik-06ethersonik-07ethersonik-08ethersonik-09

Adapters profiling : resample ratio

Server running with the ”dummy” driver and audio adapter

0.9

0.92

0.94

0.96

0.98

1

1.02

1.04

1.06

1.08

1.1

0 500 1000 1500 2000 2500 3000 3500 4000

resa

mpl

ing

ratio

audio cycles

Audio adapter timing: host [rate = 48.0 kHz buffer = 1024 frames] adapter [rate = 44.1 kHz buffer = 256 frames]

Ratio 1Ratio 2

Adapters profiling : position in ringbuffer

Server running with the ”dummy” driver and audio adapter

1400

1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

3600

0 500 1000 1500 2000 2500 3000 3500 4000

fram

es

audio cycles

Audio adapter timing: host [rate = 48.0 kHz buffer = 1024 frames] adapter [rate = 44.1 kHz buffer = 256 frames]

Frames position in consumer ringbufferFrames position in producer ringbuffer

Solaris version

Reviewer comment : why on earth would anybody seriouslyconsider Solaris for pro-audio work?

well, this version was funded by french radio RTL...OSS RME MADI 64 in/out driver developed by HannuSavolainenactually not so bad (could be caracterized using theprofiling tools) : below 80 usec max scheduling latencyusing CPU sets on a highly loaded 4 cores 2 Ghz Dellmachineso good enough for RTL needs

External contacts

RTL french radioDeveloping their entirely ”digital” radio using JACK2 onSolaris with a RME MADI 64 in/out cardProfiling tools to help caracterize real-time behaviour of thesystem

CopperLanA ”complete solution for networking all equipment in thedomains of pro-audio and music” recently presented atFrankfurt MusikMesseKlavis Technologies implemented a JACK / CopperLanbridge prototype on OSX

Native InstrumentsFuture line of NI product using JACK API natively on OSXand Windows

Specific developments on OSX and Windows

JackOSX package

integrates JACK with CoreAudio (JackRouter CoreAudiodevice, JackAU audio unit, JackVST VST plugin...)based on Jackdmp/JACK2 starting early 2008 (version0.75)5 versions released in 2008200 download/day, 1100 users on Yahoo Group

Windowsintegrates JACK with Windows ASIO (JackRouter ASIOdevice)some improvements done in QjackCtlclean installer (Romain Moret in 2008)

Contributions (1)

A lot in 2008Recent code from JACK1 : Paul Davis, Florian Faber,Torben Hohn...Nedko Arnaudov, Juuso Alasuutari for D-Bus and wafscriptsRomain Moret for NetJack2Tim Blechmann : code cleanup/optimization, SSE code...Marc-Olivier Barre for D-Bus and ”now dead” sconsscripts...

Contributions (2)

Michael Voigt : JACK2 on L4/DROPS research project

L4 : micro-kernel design and DROPS: Dresden Real-TimeOperating System Projectcode source restructuration for easier later porttiming benchmark : less than 10 usec scheduling latency(+/- 1 usec) (RT Linux is 40 usec +/- 20 usec on samemachine)future : has to be used with L4/Linux to run JACKapplications for Linux on DROPS

The future : what is still needed for 2.0 version?

MIDI bridge on all supported platforms (in progress)

JACK MIDI bridge with native API on each plaform(CoreMIDI on OSX, WinMME on Windows, ALSA MIDI(seq/raw))proposal to use the already existing Master / slave modelin backendallows to activate the MIDI backend independently from theaudio backend

NetJackboth versions should be merged

Missing port latency API?Paul and Fons proposal?

The future : what is still needed for 2.0 version? (2)

Audio device reservation schemesmoother collaboration with PulseAudiouse Lennart Poettering proposed D-Bus based reservationAPIallows JACK ALSA backend to take precedence overPulseAudio (unconditionnal reservation)available and to be tested since JACK 1.9.2 version

The future : various ideas

Multi-backend modelMaster / slave model for audio backend...

More control frontendOSC (network control: server start/stop, connectionstate...)

”libjacknet” ideapublish the NetJack API (master, slave, adapter) in aseparated ”libjacknet” libraryallows audio components to access NetJack without theneed of a JACK serversuccessfully tested on iPhone simulator (master or slave)

The future : pipelining version (1)

What is it for?allows to better use multi-cores machines with ”sequential”graphsgeneral principle : executes the graph with a buffer size ofD/N (D : driver buffer size, N : divisor)


One example

A B

A(2)A(1) A(3)

B(3)B(1)

A(4)

B(2) B(4)

Dividing the buffer by 4

Two cores running A and B


divisor can be dynamically changed, and causes a”buffer-size change” notificationclient can chose *not* to be pipelined : so hybrid graphscan be runavailable on a separated ”pipelining” branch on SVNtesting in real word situations welcome! (Ardour 2.8 isready for that...)

What's new in JACK2 - Linux Audio...

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